1. Field of the Invention
This invention relates to the diagnosis of pneumonias and more particularly to the detection of Legionella pneumophila in humans.
2. Description of the Prior Art
Legionella pneumophila causes an estimated 1% to 2% of sporadic pneumonias, 4% to 11% of diagnostically difficult pneumonias resembling viral or mycoplasma pneumonia, and, in some hospitals, a significant fraction of nosocomial pneumonias. Currently, the diagnosis of Legionella pneumophila pneumonia requires demonstration of specific seroconversion, growth of the organisms from appropriate specimens, or demonstration of organisms in clinical specimens by direct fluorescent (DF) antibody stains. Of the three diagnostic metods, only the DF antibody method is rapid; but it detects Legionella pneumophila antigen in only 24% to 75% of those persons known to have Legionnaires' disease. In cases in which the sputum DF antibody is negative, or coughed sputum cannot be obtained, examination of sputum obtained by transtracheal aspiration, lung fluid obtained by lung aspiration, or lung tissue obtained by biopsy may be required. Patients, particularly those unable to produce sputum, will benefit from an alternative noninvasive rapid diagnostic test for Legionnaires' disease, provided that such test is sufficiently specific and sensitive.
Earlier studies by Tilton, Legionnaires' Disease Antigen Detected by Enzyme-Linked Immunoabsorbent Assay, 90 Ann. Intern. Med. 697 (April 1979), and by Berdal, Farshy and Feely, Detection of Legionella pneumophila Antigen in Urine by Enzyme-Linked Immunospecific Assay, 9 J. Clin. Microbiol. 601 (1981), suggested the potential diagnostic utility of an enzyme-linked immunosorbent assay for the detection of Legionella pneumophila antigen. However, both studies were very preliminary, and both suffer fromm low sensitivity (i.e. the number of patients found to have Legionnaires' disease was comparatively low when contrasted with the number known to have the disease). The method employed by Tilton also suffers from cross-reactivity with various organisms in the urine sample other than Legionella pneumophila antigen. Neither the Tilton nor the Berdal et al method discloses the use of radioimmunossay techniques.
Accordingly, it is the principal object of the present invention to provide an improved rapid, sensitive and specific means for detecting Legionnaires' disease.
A further object of the present invention is to provide a noninvasive means for detecting Legionnaires' disease.
Another object of the present invention is to minimize the number of tests falsely indicating the presence of Legionnaires' disease.